CREATE TRIGGER SOLUTION_TECHS_TRG 
BEFORE INSERT ON SOLUTION_TECHS 
FOR EACH ROW 
BEGIN
  <<COLUMN_SEQUENCES>>
  BEGIN
    IF :NEW.SOLUTION_TECH_ID IS NULL THEN
      SELECT SOLUTION_TECHS_SEQ.NEXTVAL INTO :NEW.SOLUTION_TECH_ID FROM DUAL;
    END IF;
  END COLUMN_SEQUENCES;
END;
/
